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Commit 48ba7c3c authored by Heiner Kallweit's avatar Heiner Kallweit Committed by Jonathan Cameron
Browse files

iio: adc: meson-saradc: add calibration 



This patch adds calibration for the Meson SAR ADC.
Points 25% vref and 75% vref are used for calibration.
It uses a simple linear calibration function: SCALE * val + BIAS

Successfully tested on a Odroid C2.

Signed-off-by: default avatarHeiner Kallweit <hkallweit1@gmail.com>
Tested-by: default avatarMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: default avatarMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent 66893ea3

drivers/iio/adc/meson_saradc.c

+75 −2
Original line number Diff line number Diff line
@@ -166,6 +166,8 @@ 


#define MESON_SAR_ADC_MAX_FIFO_SIZE				32

#define MESON_SAR_ADC_TIMEOUT					100 /* ms */

/* for use with IIO_VAL_INT_PLUS_MICRO */

#define MILLION							1000000



#define MESON_SAR_ADC_CHAN(_chan) {					\

	.type = IIO_VOLTAGE,						\
@@ -173,7 +175,9 @@ 
	.channel = _chan,						\

	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\

				BIT(IIO_CHAN_INFO_AVERAGE_RAW),		\

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\

	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\

				BIT(IIO_CHAN_INFO_CALIBBIAS) |		\

				BIT(IIO_CHAN_INFO_CALIBSCALE),		\

	.datasheet_name = "SAR_ADC_CH"#_chan,				\

}
@@ -233,6 +237,8 @@ struct meson_sar_adc_priv { 
	struct clk				*adc_div_clk;

	struct clk_divider			clk_div;

	struct completion			done;

	int					calibbias;

	int					calibscale;

};



static const struct regmap_config meson_sar_adc_regmap_config = {
@@ -252,6 +258,17 @@ static unsigned int meson_sar_adc_get_fifo_count(struct iio_dev *indio_dev) 
	return FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);

}



static int meson_sar_adc_calib_val(struct iio_dev *indio_dev, int val)

{

	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

	int tmp;



	/* use val_calib = scale * val_raw + offset calibration function */

	tmp = div_s64((s64)val * priv->calibscale, MILLION) + priv->calibbias;



	return clamp(tmp, 0, (1 << priv->data->resolution) - 1);

}



static int meson_sar_adc_wait_busy_clear(struct iio_dev *indio_dev)

{

	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
@@ -302,7 +319,7 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev, 


	fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK, regval);

	fifo_val &= GENMASK(priv->data->resolution - 1, 0);

	*val = fifo_val;

	*val = meson_sar_adc_calib_val(indio_dev, fifo_val);



	return 0;

}
@@ -527,6 +544,15 @@ static int meson_sar_adc_iio_info_read_raw(struct iio_dev *indio_dev, 
		*val2 = priv->data->resolution;

		return IIO_VAL_FRACTIONAL_LOG2;



	case IIO_CHAN_INFO_CALIBBIAS:

		*val = priv->calibbias;

		return IIO_VAL_INT;



	case IIO_CHAN_INFO_CALIBSCALE:

		*val = priv->calibscale / MILLION;

		*val2 = priv->calibscale % MILLION;

		return IIO_VAL_INT_PLUS_MICRO;



	default:

		return -EINVAL;

	}
@@ -762,6 +788,47 @@ static irqreturn_t meson_sar_adc_irq(int irq, void *data) 
	return IRQ_HANDLED;

}



static int meson_sar_adc_calib(struct iio_dev *indio_dev)

{

	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);

	int ret, nominal0, nominal1, value0, value1;



	/* use points 25% and 75% for calibration */

	nominal0 = (1 << priv->data->resolution) / 4;

	nominal1 = (1 << priv->data->resolution) * 3 / 4;



	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_DIV4);

	usleep_range(10, 20);

	ret = meson_sar_adc_get_sample(indio_dev,

				       &meson_sar_adc_iio_channels[7],

				       MEAN_AVERAGING, EIGHT_SAMPLES, &value0);

	if (ret < 0)

		goto out;



	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_VDD_MUL3_DIV4);

	usleep_range(10, 20);

	ret = meson_sar_adc_get_sample(indio_dev,

				       &meson_sar_adc_iio_channels[7],

				       MEAN_AVERAGING, EIGHT_SAMPLES, &value1);

	if (ret < 0)

		goto out;



	if (value1 <= value0) {

		ret = -EINVAL;

		goto out;

	}



	priv->calibscale = div_s64((nominal1 - nominal0) * (s64)MILLION,

				   value1 - value0);

	priv->calibbias = nominal0 - div_s64((s64)value0 * priv->calibscale,

					     MILLION);

	ret = 0;

out:

	meson_sar_adc_set_chan7_mux(indio_dev, CHAN7_MUX_CH7_INPUT);



	return ret;

}



static const struct iio_info meson_sar_adc_iio_info = {

	.read_raw = meson_sar_adc_iio_info_read_raw,

	.driver_module = THIS_MODULE,
@@ -901,6 +968,8 @@ static int meson_sar_adc_probe(struct platform_device *pdev) 
		return PTR_ERR(priv->vref);

	}



	priv->calibscale = MILLION;



	ret = meson_sar_adc_init(indio_dev);

	if (ret)

		goto err;
@@ -909,6 +978,10 @@ static int meson_sar_adc_probe(struct platform_device *pdev) 
	if (ret)

		goto err;



	ret = meson_sar_adc_calib(indio_dev);

	if (ret)

		dev_warn(&pdev->dev, "calibration failed\n");



	platform_set_drvdata(pdev, indio_dev);



	ret = iio_device_register(indio_dev);